1. Field of the Invention
The present invention relates to a flat display panel and black matrix thereof, and more particularly, to an organic light emitting diode display panel having a black matrix structure with a light-shielding layer and a semiconductor layer.
2. Description of the Prior Art
Organic light emitting diode displays (OLEDs) are one type of electroluminescene (EL) display and have the advantages of high brightness, rapid response speed, light weight, low power consumption, and wide viewing angle. Therefore, OLEDs expected to replace the liquid crystal display (LCD) and the plasma display and become the mainstream.
Generally, a conducting wire pattern or electrodes made of metal in the OLED display reflect light from the environment and cause the problem of poor contrast. Therefore, a black matrix structure or a polarizing film is often installed in the OLED display to improve the poor contrast.
Please refer to FIG. 1 .FIG. 1 is a schematic diagram of a conventional black matrix structure of an OLED display. As illustrated in FIG. 1, the conventional black matrix structure 10 is formed on a substrate 20 of an OLED display. The black matrix structure 10 comprises a chromium oxide layer 12 disposed on the surface of the substrate 20, a chromium nitride layer 14 disposed on the surface of the chromium oxide layer 12, and a chromium layer 16 disposed on the chromium nitride layer 14. Another surface of the substrate 20 is the display plane of the OLED display. When the environmental light enters the substrate 20 (as the solid arrows show in FIG. 1), the black matrix structure 10 will absorb part of the environmental light to reduce the reflection (as the dashed arrows show in FIG. 1) and improve the contrast of the OLED.
However, the conventional black matrix structure includes chromium, chromium oxide, and chromium nitride, and these materials produce poisonous substances such as Cr6+ after etching processes, which may cause environment pollution. Therefore many developed countries have decided to limit the application range of the abovementioned materials. In addition, the resistance to electrostatic discharge of the conventional black matrix structure is typically insufficient, and therefore, the OLED display is easily affected and damaged by electrostatic discharge. Furthermore, although the reflection of environmental light can be effectively reduced by disposing a polarizing film on the surface of the substrate, the emitted light from the OLED itself has a transmittance of only about 43%, resulting in a reduction of brightness and an increase of power consumption. Meanwhile, the practice of the polarizing film also increases the thickness of the panel and adds a consideration for a yield rate of a coating process.